A Phase 1 Study of Vinflunine in Combination with Trastuzumab for the Treatment for HER2-positive Metastatic Breast Cancer

Objective: To determine the recommended dose (RD) of vinflunine in combination with trastuzumab in human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) and to investigate potential pharmacokinetic (PK) interactions.

Patients And Methods: In the first part of the study, two dose levels of vinflunine given every 3 weeks were explored (280 and 320 mg/m(2)) combined with trastuzumab (4 mg/kg loading dose and 2 mg/kg weekly). For each level of dose, six patients were enrolled to determine the RD for phase 2 studies (RP2S). In the second part of the study, 18 additional patients at RP2S have been evaluated to confirm safety and investigate preliminary antitumor activity.

Results: The RD was 320 mg/m(2) according to the dose escalation plan. Eleven of 15 additional patients who received this dose experienced dose-limiting toxicities, leading to a reduction in the RD to 280 mg/m(2). When compared to prior trials when vinflunine was used as a single agent, neither vinflunine total blood clearance nor trastuzumab serum concentrations were modified when the drugs were combined. All patients were evaluable, and the overall response rate was 73.3 % (95 % CI 54.1-87.7). The median progression-free survival was 11.3 months (95 % CI 9.4-21.0). At the dose of 280 mg/m(2), grade 3-4 neutropenia were seen in 4 patients (44.4 %) without febrile neutropenia. Non-hematologic grade 4 toxicities were not reported while grade 3 peripheral sensory neuropathy concerned 2 patients (22.2 %).

Conclusion: The RD of vinflunine in combination with the standard regimen of trastuzumab is 280 mg/m(2) every 3 weeks. No mutual PK drug-drug interaction was seen. This regimen appears to be active with a favorable safety profile. Its role in HER2-positive MBC treatment needs to be defined in prospective comparative clinical trials.